This study will examine neuropsychological dysfunction and hypermotility in adolescent Substance Use Disorder (SUD), which frequently are morbid with Conduct Disorder (CD) and Attention-Deficit Hyperactivity Disorder (ADHD). Among youth with SUD the applicants will determine whether those with CD+ADHD have more serious pathology: earlier onset of CD symptoms, neuropsychological abnormalities, hypermotility, and a more persistent course. The applicants will study circadian rhythms of motility and neuropsyhological assessments to clarify aspects of ADHD contributing to SUD severity. They will compare 200 male and female patients and 200 controls in 48-hour assessments of motility, as subjects engage in activities and testing. Neuropsychological tests will assess verbal performance skills, impulsivity, inattention, and risk-taking. Diagnoses and severity of CD, ADHD, depression, and anxiety will be determined. Subjects, parents, and teachers will contribute information. Hypotheses focus on contributions to SUD from aspects of ADHD and CD: (1) Adolescents boys with CD and SUD will differ (after controlling for age) from community controls in having (a) greater spontaneous motility levels, (b) poorer neuropsychological functioning, including more impulsivity, inattention, and risk-taking in a laboratory reward- punishment paradigm, (c) more experiences of abuse and neglect, and (d) higher prevalence of psychiatric disorders (in addition to CD and SUD). (2) There are almost no data from girls with CD and SUD on abnormalities of motility, inattention, impulsivity; or on deficits in executive function, verbal processing, or verbal memory; on risk-taking or abuse/neglect experiences; or on severity of depression and anxiety. The applicants propose to disprove the null hypotheses of no main effect of gender, no main effect of group (patient or control), and no interactions, of those variables. The paucity of data on CD+SUD girls prevents directional predictions regarding gender effects. (3) Among male and female patients referred for treatment of CD and Substance Dependence (after controlling for age, gender, and severity of CD), the severity of the substance involvement will associate separately and jointly with: (A) Measures associated with comorbid CD + ADHD: (1) Greater motility, (2) Poorer neuropsychological functioning in selected areas (impulsivity, inattention, and "executive functions" including risk-taking). (B] Earlier onset of CD. (C) Greater depression. That is, we predict that among substance-dependent adolescents, those with earlier CD onset, more severe ADHD-related symptoms, more neuropsychological deficits, and more depression will have more substance involvement.